Wikipedia says: 'Epigenetics is the study of epigenetic inheritance, a set of reversible heritable changes in gene function or other cell phenotype that occur without a change in DNA sequence (genotype).'

That's a pretty general definition, and you can get into some pretty good arguments that this or that word should be changed.

The fundamental discoveries that began the field began to be discussed in 1941, but it grew slowly until fairly recent years. By 2004 the science had developed enough that the 69th Cold Spring Harbor Symposium on Quantitative Biology covered the topic. Many of the authors of this book attended that symposium and the seeds for this book were sown.

The book was written by about forty of the preeminent researchers in the field. It consists of 24 chapters covering virtually all known aspects of the subject. It can serve as a reference work for the current state of the art, or could be used as a text for advanced undergraduate or graduate courses on gene regulation.